Split prolongpointstru into search-only (prolongpointstru_search) and
append-only (prolongpointstru_append) functions. The search is read-only
and thread-safe; each thread builds private linked lists via
prolongpointstru_append, merged after the parallel loop.
This eliminates critical-section contention and delivers ~2.2x speedup:
setupintintstuff: 511s -> 252s, total init: 592s -> 267s.
Also add -qopenmp to ShellPatch.o compilation via makefile override rule
and <omp.h> include with _OPENMP guards + fallback stubs.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
